The middleman contacted the private detective Ben Zuidema, who was originally hired to investigate the theft, and apparently offered him €1m to facilitate the deal.
But instead Mr Zuidema passed the information to police investigators and the eight works were then recovered in a sting operation.
Three suspects were arrested: a 45-year-old German man who lives in Dubai, his 62-year-old mother from Belgium and a 66-year-old man from Walem.
The paintings were by Pierre-Auguste Renoir, Camille Pissarro, David Teniers, Willem van de Velde (two works), Jan Brueghel the Younger, Eva Gonzalès and Paul-Desiré Trouillebert. A ninth missing painting from the same collection is believed to have been destroyed.
Robert Noortman, who died of a heart attack aged 60 in 2007, had insured the works shortly before their disappearance and received a payout of 5m guilders (£2m) after the theft.
Noortman Master Paintings were bought by Sotheby’s in June 2006, who acquired all the assets of the business including $26m of debts.